Cellulose organic acid ester plastics containing symmetrical diphenyl urea



United States Patent Ofiice 2,848,341 Patented Aug. 19, 1958 CELLULOSE ORGANIC ACID ESTER PLASTICS gglEZAINING SYMMETRICAL DIPHENYL William M. Gearhart and Harry R. McAmis, Kingsport,

Tenn., assignors to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey No Drawing. Application April 23, 1954 Serial No. 425,316

'3 Claims. (Cl. 106-406) This invention relates to cellulose organic acid ester plastics, and more particularly to the stabilization of such plastics.

As is well known in the art, plastics having excellent properties for a great many purposes can be prepared from cellulose organic acid esters, such, for example, as cellulose acetate, cellulose propionate, cellulose butyrate, cellulose acetate-propionate and cellulose acetate-butyrate, with suitable plasticizers. Many examples of suitable plasticizers are shown in the art. The choice of plasticizers forms no part of our invention.

However, cellulose organic acid ester plastics have not been entirely suitable for use in places where they are exposed to a considerable amount of ultraviolet light; e. g., out of doors. After one or two months of outdoor exposure in a sunny climate, the plastic bleached and otherwise known as carbanilide, to a cellulose organic acid ester plastic composition strongly inhibits breakdown of the resulting plastic by exposure to ultraviolet light. We prefer to use approximately 0.5% to 1.5% of s-diphenyl urea, based on the weight of cellulose organic acid ester. Higher amounts give only slightly greater weathering resistance, and may change the physical properties .of the plastic. As cellulose organic acid esters, we have employed those mentioned above, in which the acyl groups contain from 2 to 4 carbon atoms. Cellulose acetate plastics are not as effective for outdoor uses as are the mixed and higher esters, that is, those containing an acyl group higher than acetyl, because the usual cellulose acetate plasticizer retention is rather poor under outdoor exposure.

In testing our cellulose organic acid ester plastics containing s-diphenyl urea, we have tested sheets of, 0.050" thickness by the Kline test, designated as A. S. T. M. D795-49. The method consists of the following test cycle:

18 hours under General Electric S-l sunlamp (6 inches below lamp) 2 hours in fog chamber 2 hours under S-1 sunlamp 2 hours in fog chamber This cycle was repeated until the first sign of surface failure of the samples of plastic, as shown by dulling, chalking, checking, crazing, warping, or discoloration. The temperature inside the accelerated weathering machine is maintained at 55 to 60 C;

It has been found by the National Bureau of Standards and verified by us, that roughly 200 hours sunlamp exposure by this test is equivalent to one years outdoor exposure in Washington, D. C. Outdoor exposure farther south or at high altitude is more severe, however.

The following table shows the values obtained by weathering similar samples of plasticized cellulose acetate-butyrate plastics of the same composition, containing (a) no ultraviolet inhibitor, (b) 1%, based on the cellulose ester, of the well-known ultraviolet inhibitor, phenyl salicylate, and (c) 1%, based on the cellulose ester, of s-diphenyl urea.

The numbers in the Color of Plastic column indicate the relative intensity of coloration of the samples.

At the end of 840 hours, the sample containing the s-diphenyl urea showed slight checking of the surface.

s-Diphenyl urea is advantageously introduced into a cellulose organic acid ester plastic at the time the cellulose ester is compounded with the plasticizer. This compounding may be accomplished by any of the known methods, including the method of working on hot rolls described in Conklins U. S. Patent 2,155,303. s-Diphenyl urea causes no substantial discoloration of the plastic, even when the hot-rolling method of compounding is employed, and no substantial discoloration takes place during accelerated testing.

By way of application, we give the following example of making up cellulose organic acid ester plastics containing s-diphenyl urea. It will be understood that this illustration does not constitute a limitation of our invention, which is defined in the appended claims.

Example.l00 parts of cellulose acetate-butyrate containing approximately 12% acetyl and 37% butyryl is intimately mixed in a sigma-blade mixer with 13 parts of dibutyl sebacate and 1 part of s-diphenyl urea. The mixture is worked on hot rolls by the method described in the Conklin Patent 2,155,303. The resulting plastic can then be granulated and be ready for any molding or extrusion operation.

Any of the known plasticizers for cellulose organic acid esters, such, for example, as dibutyl phthalate, dibutyl sebacate, methoxyethyl stearate, tricresyl phosphate, butoxyethyl phthalate, diamyl phthalate, ethyl p-toluene sulfonamide, etc. may be used. In the case of the softer cellulose esters, such as cellulose acetate-butyrate, plastics may even be formed without the use of any plasticizer.

What we claim as our invention and desire to be secured by Letters Patent of the United States is:

1. A cellulose organic acid ester plastic for molding and extrusion comprising a cellulose organic acid ester selected from the group consisting of cellulose acetate, cellulose propionate, cellulose butyrate, cellulose acetatepropionate and cellulose acetate-butyrate, a plasticizer therefor, and, as an agent for inhibiting deterioration of the plastic by ultraviolet light, approximately 0.5% to 1.5%, based on the weight of the cellulose ester, of s-diphenyl urea.

2,848,341 3 4 2. A cellulose acetate-butyrate plastic for molding and References Cited in the file of this patent extrusion comprising cellulose acetate-butyrate, a plasticizer therefor, and, as an agent for inhibiting deteriora- UNITED STATES PATENTS tion of the plastic by ultraviolet light, approximately 1,302,202 Nathan et al Apr. 29, 1919 0.5% to 1.5%, based on the weight of the cellulose 5 1,460,097 Donohue et al. June 26, 1923 acetate-butyrate, of s-diphenyl urea. 1,654,114 Davis Dec. 27, 1927 3. A cellulose acetate-butyrate plastic comprising cellu- 1,867,658 Dreyfus July 19, 1932 lose acetate-butyrate and, as an agent for inhibiting de- 2,155,303 Conklin Apr. 18, 1939 terioration of the plastic by ultraviolet light, approx 2,393,802. Morey et a1. Jan. 29, 1946 mately 0.5% to 1.5%, based on the weight of the cellu- 10 2,683,132 Young et a1. July 6, 1954 lose acetate-butyrate, of s-diphenyl urea. 2,683,172 Hill et a]. July 6, 1954 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No, 2,848,341 August 19, 1958 William M, Gearhart et a1,

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below Column 3, line '7, for "plastic comprising" read plastic for molding and extrusion comprising Signed and sealed this 28th day of October 1958.,

(SEAL) Attest:

KARL H, AXLINE ROBERT C. WATSON Attesting Ofiicer Commissioner of Patents UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 2,848,341 August 1% 195a William M, Gearhart et alo It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction and that the said Letters 5 Patent should read as corrected below.

Column 3, line '7, for "plastic comprising" read plastic for molding and extrusion comprising Signed and sealed this 28th day of October 1958o (SEAL) Attest:

KARL H, AXLINE ROBERT C. WATSON Attesting Ofiicer Commissioner of Patents UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 2,848,341 August 19,1958

William Mo Gearhart et all,

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 3, line '7, for plastic comprising" read plastic for molding and extrusion comprising Signed and sealed this 28th day of October 19580 (SEAL) Attest: KARL AXLINE ROBERT C. WATSON Attesting Ofiicer Commissioner of Patents 

1. A CELLULOSE ORGANIC ACID ESTER PLASTIC FOR MOLDING AND EXTRUSION COMPRISING A CELLULOSE ORGANIC ACID ESTER SELECTED FROM THE GROUP CONSISTING OF CELLULOSE ACETATE, PROPIONATE AND CELLULOSE ACETATE-BUTYRATE, A PLASTICIZER PROPIONATE AND CELLULOSE ACETATE-BUTYRATE, A PLASTICIZER THEREFOR, AND, AS AN AGENT FOR INHIBITING DETERIORATION OF THE PLASTIC HY ULTRAVIOLETE LIGHT, APPROXIMATELY 0.5% TO 1.5% BASED ON THE WEIGHT OF THE CELLULOSE ESTER, OF S-DIPHENYL UREA. 